The powering up of several modules in an electronic system may be a delicate process. In many cases, the modules should not be powered on at the same time because it may cause damage to one or more modules, improper or unintended operations, inefficient use of power, and other undesirable effects. Often instead, the powering on (as well as powering off) of modules requires a precise predetermined sequence. Generally, a power distributing sequencer is employed to perform this operation.
Typically, a power distributing sequencer controls a plurality of voltage regulators in order to supply voltages to various modules of an electronic system. Often, some of these regulators supply several voltages to an applications processor, and other modules depending on the configuration and function of the electronic system. For example, if the electronic system is a cellular telephone, the system may further include memory, audio circuitry, display, radio frequency (RF) chipset, digital signal processor, and others. The power distributing sequencer is typically hardwired to apply a predetermined power on sequence for a specific applications processor. Once the processor has been powered on, the processor provides discrete instructions to the sequencer on how and when to power up and down the respective modules of the system.
Because the power distributing sequencer is hardwired for a specific applications processor, if the system manufacturer decides to use another type of processor, then a new power distributing sequencer needs to be designed that will work properly with this type of processor. This has the adverse consequence of a long lead design and manufacturing cycle for the sequencer, which, in turn, delays the development and manufacturing of the electronic system. Furthermore, lots of interactions and time are spent between the sequencer manufacturer, processor manufacturer, and system manufacturer in order to properly design the sequencer so that it applies the appropriate power on and off sequences to the processor. This is generally a time consuming and expensive process. Moreover, if the system manufacturer has several products that uses different applications processors, the system manufacturer, as well as the sequencer manufacturer, have to manage and keep track of different types of sequencers, which complicates inventory.